Biased cosmological parameter estimation with galaxy cluster counts in the presence of primordial non-Gaussianities

TL;DR

This paper investigates how assuming Gaussian initial conditions when analyzing galaxy cluster counts can bias cosmological parameter estimates, especially for the dark energy equation of state and primordial perturbation amplitude.

Contribution

It quantifies biases in cosmological parameters caused by neglecting primordial non-Gaussianities in galaxy cluster count analyses.

Findings

Biases in dark energy parameter w can be significant.

Neglecting non-Gaussianities affects amplitude estimates of primordial perturbations.

Cluster counts may reconcile different measurements of primordial perturbations.

Abstract

The redshift dependence of the abundance of galaxy clusters is very sensitive to the statistical properties of primordial density perturbations. It can thus be used to probe small deviations from Gaussian initial conditions. Such deviations constitute a very important signature of many inflationary scenarios, and are thus expected to provide crucial information on physical processes which took place in the very early Universe. We have determined the biases which may be introduced in the estimation of cosmological parameters by wrongly assuming the absence of primordial non-Gaussianities. Although we find that the estimation of the present-day dark energy density using cluster counts is not very sensitive to the non-Gaussian properties of the density field, we show that the biases can be considerably larger in the estimation of the dark energy equation of state parameter $w$ and of the amplitude of the primordial density perturbations. Our results suggest that a significant level of non-Gaussianity at cluster scales may be able to reconcile the constraint on the amplitude of the primordial perturbations obtained using galaxy cluster number counts from the Planck Sunyaev-Zeldovich Catalog with that obtained from the primary Cosmic Microwave Background anisotropies measured by the Planck satellite.